This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Vitamin K epoxide reductase (VKOR) generates vitamin K hydroquinone to sustain gamma-carboxylation of many blood coagulation factors. The enzyme is also the target of warfarin, the most commonly used oral anticoagulant. Homologs of VKOR have been discovered in many organisms, including bacteria. In bacteria, VKOR is involved in disulfide bridge formation. The goal of the project is to determine the structure of a bacterial homolog of VKOR. This would allow insight into the mechanism of electron transfer and shed light on the mechanism of warfarin inhibition.